Genetic diversity and population structure of Hibiscus aridicola, an endangered ornamental species in dry-hot valleys of Jinsha River.

Hibiscus aridicola is an endangered ornamental shrub of the family Malvaceae that is endemic to the dry-hot valleys of Jinsha River in southwestern China. This species is a typical plant species with extremely small populations (PSESP). To support and monitor future conservation, develop management measures, and genotype this species, we performed extensive field studies together with genetic analyses. Specifically, we screened eleven microsatellite loci of 69 individuals of H. aridicola from four accessions. The population genetics analyses indicated that H. aridicola possesses high genetic diversity at both the population (0.6962-0.7293) and species level (0.7837) compared to other endemic/endangered species in China. The low differentiation of populations (Fst = 0.0971) and the high gene flow between populations of H. aridicola (Nm = 2.3236) could be due to its distribution along rivers in the hot-valleys of the Jinsha River and the wind-mediated dispersal of its seeds. Furthermore, the genetic diversity of H. aridicola is slightly positively correlated with geographic distance. Two populations are undergoing a genetic bottleneck, and require more specific attention from conservationists. Additionally, our analyses of the population genetics of H. aridicola demonstrate that the declines in populations are not the result of the internal genetics of these populations but due to external human activities over the past decades.